A standard cross country ski has a forwardly tapering and pointed tip or shovel, a rearwardly tapering heel or tail, and a central portion of substantially unchanging transverse width, that is measured perpendicular to the longitudinal centerline of the ski and parallel to its upper and lower faces. Such a ski is typically used with bindings permitting the skier's foot to pivot relative to the ski about one or more axes also perpendicular to the ski centerline and parallel to the horizontal ski faces.
In use such a ski merely follows the tracks of the cross-country trail with the user kicking and poling on alternate sides to propel himself or herself along with the skis always in the tracks and parallel to the travel direction. A modified system uses a ski whose side edges are slightly oppositely concave, that is forming oppositely outwardly open arcs.
Recently however a new style of cross-country skiing termed "skating" has been developed which allows a skier to move on the level and even uphill at a much greater speed than has hitherto been possible. This method, like its namesake sport, entails pushing with one ski at a time, and the pushing ski is angled somewhat to the displacement direction and to the other ski which itself acts purely as support and guide. Thus the skier bites into the snow or ice with the inside edge of one ski and pushes himself along. The skier can alternate each push from one side with a push from the other, or can take a few smaller pushes with one side alternating with a few small pushes with the other side.
In order to adapt standard cross-country skis to this style of skiing, several modifications to the known skis have been suggested, to wit:
The central zone of the ski is made more rigid.
The curve of the ski is changed since any wax or the like used for holding is useless in view of the transverse action of the pushing ski.
The ski is made shorter to increase its maneuverability.
The shovel of the ski is made shorter to lighten the ski and make it easier to recover.
In spite of these modifications normal skis with parallel edges are not well adapted to skating style. At each lateral push the pushing ski slips somewhat between the shovel and the boot, particularly if the snow is hard and frozen as is often the case. This slipping is worse as speed increases and as the surface is icier. Not only does this slipping cut down on maximum speed, an effect that is increased as travel speed increases, but it also can lead to a dangerous fall in situations where the pushing ski kicks out altogether on a very hard push.
Other changes have been made to eliminate this effect, namely:
The ski is made to be very square over a portion of its length.
A metallic reinforcing plate is provided in the ski to rigidify it and serve as gripping edge.
Longitudinal grooves are formed that extend along the ski.
The ski is made more resistant to torsional deformation.
Finally the ski has been redimensioned so it is in one system 44 mm wide in the center, 46 mm at the shovel, and 45 mm at the tail, and in another system it is 44 mm at the shovel, 46 mm at the boot in the center, and 42 at the tail.
None of these modifications produces a ski suitable for skating with limited slipping of the front end and good maneuverability.